The objective of this study is to simulate combustiuon process and pollutant formation in the combustion chamber of a DI diesel engine. The modelled results were validated by comparing predictions against corresponding experimental data for a diesel engine. The predicted and measured in-cylinder pressure and emission data were in good agreement. Computational fluid dynamics (CFD) is able to significantly reduce the number of experimental test and measurement and lower the development time and costs. Some parameter which are needed for CFD calculation must be achieved experimentally such as turbulence time scale constant. The CFD simulations demonstrated good agreement to the measured data. The results show that, applying appropriate constant of each combustion model including eddy break up model (Ebu), caracteristic timescale model (Ctm) and extended coherent flamelet model (Ecfm) causes the computaional result to be in agreement with experimental results. Furthermore the result show that the nearest prediction in comparasion with experimental result is by applying the Ecfm model.